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Optical observations of Io's neutral clouds and plasma torus

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Abstract

A review of ground-based optical observations of Io's neutral clouds and plasma torus is provided. The physical processes determining the spatial distribution and intensity of torus emissions are described with reference to a model based on Voyager spacecraft data. The model is then compared to ground-based observations. Inconsistencies and variations in torus conditions over long timescales are emphasized. Periodicities in the torus evident in Voyager and ground-based are critically discussed.

Processes determining the spatial characteristics of the neutral clouds are discussed. Observations of the slow sodium cloud are compared to model calculations. Special attention is paid to recent observations of high velocity neutrals and species in the upper atmosphere of Io itself. The article concludes with suggestions for future observations and research.

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Thomas, N. Optical observations of Io's neutral clouds and plasma torus. Surv Geophys 13, 91–164 (1992). https://doi.org/10.1007/BF01903525

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